Molecular sieve monoliths, such as zeolite monoliths find use in catalytic applications such as catalysts, catalyst supports, or adsorbing structures, where they must be strong and of uniform composition throughout the body. Depending on their pore size, they are suitable for adsorbing various molecular size contaminants or for catalyzing various chemical reactions, or for moisture removal. They are made by shaping e.g. extruding plasticized mixtures of the molecular sieve and various binders and vehicle such as water. One effective binder is silicone resin. Ordinarily the silicone resin is dissolved in a solvent as described in U.S. Pat. Nos. 4,631,267 and 5,633,217. For hydrophobic molecular sieves such as e.g. ZSM zeolites, this poses no problem. However, with hydrophilic molecular sieves, repelling of the silicone resin binder solution poses a problem. For example, in forming a plasticized batch of a hydrophilic zeolite small pore such as A4 zeolite with silicone resin dissolved in a solvent, the batch becomes soft and gummy upon addition of the silicone resin solution prior to addition of the water vehicle. Though rods and ribbons can be extruded, the products are so gummy and soft that it is impossible to maintain their shapes for further processing.
When the monoliths are honeycombs especially honeycombs with thin walls, it is even more important that the plasticized mixture be stiff and able to maintain its shape, otherwise the honeycomb walls will collapse.
U.S. Pat. No. 5,492,883 relates to shaping zeolites using a silicone resin emulsion as a binder. However, the zeolites are medium to large pore size.
It would be desirable to have a method of shaping plasticized mixtures of small pore molecular sieves wherein the shaped products would have strength in both the green state and the final heat-treated structure.